Transition issues are very important in a RR. You have to assume that
old software will be around for quite a long time. Someone is bound
to be using old code for a very long time.
I'm not disputing that. What I am suggesting is that if there was a
version number (say) negotiation mechanism then new code could negotiate
for support of new features with a server but without this a new server
would return old style data (which will avoid the old code barfing).